Problem Description

Cisco has discovered a major software defect that can affect customers deploying Voice solutions, including Cisco CallManager, Cisco SRS Telephony or Cisco CallManager Express on the IAD243X, 1751/1760, 2600XM, 2691, 3600, 2800, 3700 or 3800 platforms. The major issue affecting customers are documented in this notice.

DSP hangs with more than one active call on analog FXO lines

When there is an active call on one FXO port and a second call is attempted on another FXO port, the active call may be dropped. After the active call is dropped, the DSP hangs and any voice port that uses the DSP is unable to send or receive any calls. This problem has been replicated on routers running Cisco IOS Software version 12.3(11)T with the following network module combinations:

NM-HD-1V and VIC2-2FXO or VIC2-4FXO

NM-HD-2V and VIC2-2FXO or VIC2-4FXO

NM-HD-2VE and VIC2-2FXO or VIC2-4FXO

NM-HDV2 and VIC2-2FXO or VIC2-4FXO

NM-HDA-4FXS and EM-HDA-4FXO

EVM-HD-8FXS/DID and EM-HDA-6FXO or EM-HDA-3FXS/4FXO

Customers using Cisco IOS Software version 12.3(8)T4 or below have not reported this problem.

Background

This issue has been observed on routers running Cisco IOS Software version 12.3(11)T with supervisory-disconnect anytone configured under the FXO voice port settings.

In addition, this issue has been replicated when supervisory-disconnect anytone and any of the following echo-cancel commands are configured under the voice port.

When multiple calls are placed across multiple FXO ports simultaneously, active calls may become disconnected and the DSP may hang. When a DSP is in hung state, any voice port that uses that DSP cannot send or receive calls until the DSP is manually reset from the router CLI.

To check if a customer router has the susceptible hardware, enter the show diagnostics command. If the output contains a combination of any of the network modules listed above, the router may be vulnerable.

Problem Symptoms

When there is an active call on one FXO port and a second call is attempted on another FXO port, the active call may be dropped. After the active call is dropped, the DSP hangs and any voice port that uses the DSP is unable to send or receive any calls. This problem has been replicated on routers running Cisco IOS Software version 12.3(11)T with the following network module combinations:

NM-HD-1V and VIC2-2FXO or VIC2-4FXO

NM-HD-2V and VIC2-2FXO or VIC2-4FXO

NM-HD-2VE and VIC2-2FXO or VIC2-4FXO

NM-HDV2 and VIC2-2FXO or VIC2-4FXO

NM-HDA-4FXS and EM-HDA-4FXO

EVM-HD-8FXS/DID and EM-HDA-6FXO or EM-HDA-3FXS/4FXO

Customers using Cisco IOS Software version 12.3(8)T4 or below have not reported this problem.

Workaround/Solution

Cisco IOS Version 12.3(11)T1, which will incorporate a fix for this defect, will be posted in the next 30 days. Once 12.3(11)T1 is posted to Cisco.com, customers will be advised to update to this version. Additionally, customers experiencing this one way or no audio defect should open a TAC case to stay current with available options.

Until the rebuild with the fix for this defect is posted and this advisory is updated with additional information, the following steps are recommended for customers to address this issue:

Do not configure supervisory-disconnect anytone under the voice port.

Use IOS release 12.3(8)T4 or lower.

To recover a hung DSP, use the procedure below:

Find the DSP ID using show voice dsp command. The dsp id is listed under DSP NUM column.